For Mario's movement, I referenced an image I found that detailed his various speed and acceleration values for every possible state. I also wrote a Lua script for FCEUX which would show me the position and speed values of enemies in real-time. For more complicated behaviors like Bowser, I referenced a disassembly of the game. For most everything else, I stepped the emulator frame-by-frame to carefully observe the game's behavior.

If you are interested in the source, I recently uploaded it to Mario Fan Games Galaxy.

I don't see how this could "look like spam". This also happened with another game I tried to comment on (the really horrible Mario game that is somehow in the top 5 on the arcade). I think the website may have banned me after this last attempt to post a comment.